Andrew Little announced on Thursday there has been a set back with the Pike River Mine re-entry due to elevated oxygen levels at the far end of the drift.
The minister described the elevated levels as "unpredicted and unexplained," and because of this, the mine will not be entered, although there will still be an event for families.
"If you can't explain it, you stop what you're doing until you can," he said.
The shift in oxygen levels means the atmosphere in the drift has changed and the air is no longer breathable.
Little said on Thursday he could not predict how long the delay would be on re-entry, and didn't wish to speculate.
"It could be days, could be weeks," he told media.
The mine was due to be re- entered on Friday, but the families of the victims will have to wait even longer.
"It's been nearly nine years. Disappointing for the family, I feel for them most. But obviously we're going to prioritise safety first," said Little.
Newshub.
